Camera systems of the present type are used above all in laser trackers. Laser trackers according to the prior art are usually embodied having an optical image acquisition unit having a two-dimensional, light-sensitive array, for example, a CCD or CID camera or a camera based on a CMOS array, or having a pixel array sensor and having an image processing unit. The laser tracker and the camera are installed one on top of another in this case in particular such that their positions are not variable in relation to one another. The camera is, for example, rotatable together with the laser tracker about its essentially vertical axis, but is pivotable up-and-down independently of the laser tracker and is therefore arranged separately from the optics of the laser beam in particular. In particular, the camera can have a fisheye lens and therefore pivoting of the camera can be avoided or is at least necessary to a restricted extent because of a very large image acquisition range of the camera. Furthermore, the camera—for example, in dependence on the respective application—can be embodied as pivotable about only one axis. The camera can also be installed in an integrated construction with the laser optics together in a shared housing.
With the acquisition and analysis of an image—by means of an image acquisition and image processing unit—of a so-called measuring aid instrument having markings, the relative location of which to one another is known, an orientation in space of an object (for example, a probe), which is arranged on the measuring aid instrument, can be concluded. Together with the determined spatial position of the target point, furthermore the position and orientation of the object in space can be precisely determined absolutely and/or in relation to the laser tracker.
The object, the position and orientation of which are measured using the mentioned measuring device, therefore does not have to be the object itself, but rather can be the measuring aid instrument. As a part of the measurement system, for the surveying, it is moved into a position which is mechanically defined in relation to the target object or is determinable during the surveying, wherein the position and optionally the orientation of the object—for example, a measuring probe—can be concluded from its surveyed position and orientation.
Such measuring aid instruments can be embodied by so-called scanning tools, which are positioned having the contact point thereof on a point of the target object. The scanning tool has markings, for example, light spots, and a reflector, which represents a target point on the scanning tool and can be targeted using the laser beam of the laser tracker, wherein the positions of the markings and the reflector in relation to the contact point of the scanning tool are precisely known. The measuring aid instrument can also be, for example, a handheld scanner, which is equipped for distance measurement, for contactless surface surveying, wherein the direction and position of the scanner measurement beam used for the distance measurement are precisely known in relation to the light spots and reflectors which are arranged on the scanner. Such a scanner is described, for example, in EP 0 553 266 A1.
An acquisition direction of the camera is progressively aligned for the determination of the orientation of the measuring aid instrument such that an image can be acquired in the direction of the tracking beam of the laser tracker.
The camera can furthermore have a zoom function, wherein an enlargement stage can be set in dependence on the determined distance between laser tracker and target point or measuring aid instrument (vario-camera). Using these two adaptation functions (alignment and enlargement), the camera can therefore progressively acquire an image, in which the measuring aid instrument and in particular the light spots of the measuring aid instrument are imaged. An electronically analyzable two-dimensional image of a spatial arrangement of light spots thus results.
Such a measuring device having a laser tracker and an image acquisition unit for the determination of position and orientation of objects in space, on which light spots and reflectors are arranged, is described, for example, in U.S. Pat. No. 5,973,788.
A guide system for zoom systems is disclosed in EP 1 510 846 A1, using which optical assemblies, such as lenses or lens groups, are to be displaced along the optical axis of the zoom system. In this case, a carriage, which is implemented to accommodate an optical assembly, in particular a lens or lens group, has on its outer side multiple contact surfaces for contact on the internal diameter of a lens. A spindle curve is provided as a drive unit for a defined movement of the carriage. Since no direct feedback of the actual linear position occurs, but rather it can only be derived via counting of steps of the motor, inaccuracies can occur as a result of the aging process of the motor, if a motor step increases or decreases—even minimally—due to wear. It is also possible that—for example, due to a shock of the device—a step will be executed, which is not counted. This can have the result that a carriage is located at a different position than is assumed by the system, which can cause fuzzy images and measurement errors, on the one hand, and can also cause damage to the device, on the other hand.